The subject of the invention is a method for plant-protection treatment by leaf absorption, using a combination between an active ingredient and a modified oil and a novel combination for using said method.
The use of oils is very widespread in the plant-protection domain; they are used either as formulation adjuvants, to increase the efficacy of the active substances, or as coformulants. Most of the oils used are of petroleum origin and are formulated with surfactants containing aromatic nuclei such as ethoxylated alkylphenols. However, surfactants containing an aromatic nucleus are not rapidly biodegradable and damage the ecosystems. For this reason, the use of rapeseed oil or of methyl esters of rapeseed oil is now growing; however, this oil is difficult to formulate, it is a less satisfactory solvent for the active ingredient than oils of petroleum origin and, since it does not possess intrinsic surfactant properties, it has to be used in combination with surfactants containing an aromatic nucleus. In the international patent application, published under the number WO 96/22109, ethoxylated fatty acid esters are described as self-emulsifiable compounds which can be used in formulations of plant-protection active ingredients such as ethephon or chlorpropham; however, nothing is written or suggested on the activity of the compositions resulting from this combination. However, the penetration of the plant-protection active ingredient into the plant occurs either at the level of the leaves, through leaf absorption, or at the level of the roots, through radicular absorption; it is known furthermore that leaf absorption of an active ingredient is often difficult; it is observed that after seventy-two hours, up to 95% of the active ingredient is still not absorbed by the plant. A period of rain following the treatment of a crop therefore risks inducing pollution of the site, while a period of sunshine can cause the degradation of the active ingredient. The work by C. Gauvrit and F. Cabanne [Pesticide Science, 37, 147-153 (1993)] has recently made it possible to demonstrate that the increase in the efficacy of herbicides in the presence of oils is attributed to a spreading of the droplets deposited at the surface of the leaves, and to a better leaf penetration of the herbicidal active ingredient. However, these effects, for the oils used up until now, only manifest themselves markedly on plants containing crystalline cuticular waxes, such as for example the Gramineae, whereas on the amorphous cuticular waxes of dicotyledons, the effects of these oils are more modest [C. Urvoy, M. Pollacsek and C. Gauvrit, Weed Research, 32, 375-383 (1992); I. Serre, F. Cabanne and C. Gauvrit, Medelingen van de Facultelt Landbouwwentenschappen Rijksuniversiteit Gent 58/3a, 795-802 (1993)]. Starting from the hypothesis that oils can increase the leaf penetration of the products by acting on the availability of the active substances at the surface of the leaf and on the mobility of the substances in the diffusion barrier which the plant cuticle constitutes [I. Serre, University of, Grenoble thesis (1996); I. Serre, F. Cabanne and C. Gauvrit, British Crop Protection Conference 7B-3, 807-812 (1996)], the applicant has thus sought to develop a method of plant-protection treatment by leaf absorption which allows, in a short time, a high level of absorption of the active ingredient by the plant while limiting the nuisances to the ecosystems, by the use of a composition which is sufficiently effective as solvent for the active ingredient and sufficiently stable over time to be marketable.
The subject of the invention is a method of plant-protection treatment by leaf absorption, characterized in that it uses a composition comprising at least one plant-protection active ingredient and at least one modified oil.
The expression modified oil denotes either alkoxylated or else and in particular ethoxylated and/or propoxylated oils, or alkoxylated alkyl esters of the oils and in particular ethoxylated and/or propoxylated methyl, ethyl, linear or branched propyl, or linear or branched butyl esters of said oils. According to a specific aspect of the present invention, the ethoxylated oils or the ethoxylated alkyl esters of vegetable oils each have an ethylene oxide number, called in the text which follows EO value, of between 1 and 50.
The modified oils used in the context of the present invention may be of mineral, plant or animal origin. Among the modified oils of mineral origin which may be used in the method as defined above, there are in particular the modified oils of petroleum origin; among the modified oils of animal origin which may be used in the method as defined above, there is in particular modified tallow oil; among the modified oils of plant origin which may be used in the method as defined above, there are, for example, modified sunflower, linseed, castor, soybean, corn, groundnut, copra, olive, palm, hydrogenated palm or rapeseed oils.
The expression at least one modified oil indicates that the composition used in the method which is the subject of the present invention may comprise either a single modified oil or a mixture of several modified oils; in the latter case, this may include a mixture of modified oils of the same origin or a mixture of modified oils of different origins.
The expression plant-protection treatment is understood to mean in the context of the present invention preferably a fungicidal, insecticidal or herbicidal treatment.
According to a specific variant of the method as defined above, the plant-protection composition used contains at least one modified vegetable oil, alone or in the form of a mixture with one or more modified oils of the same origin or of different origins.
According to another specific variant of the method as defined above, the plant-protection composition used contains, in addition, an unmodified vegetable oil or a mixture of unmodified vegetable oils. The expression unmodified vegetable oil is understood to mean vegetable oils or their alkyl esters, such as for example the methyl, ethyl, linear or branched propyl, or linear or branched butyl esters.
According to another aspect of the present invention, its subject is a composition comprising at least one plant-protection active ingredient, at least one modified vegetable oil and at least one unmodified oil.
The unmodified oil contained in the above composition is an oil of plant, animal or mineral origin. The expression unmodified oil is understood to mean oils or their alkyl esters, such as for example the methyl, ethyl, linear or branched propyl, or linear or branched butyl esters.
The subject of the invention is more particularly a composition as defined above in which the oil or the mixture of unmodified oils is of plant origin and is preferably chosen from sunflower, linseed, castor, soybean, corn, groundnut, copra, olive, palm, hydrogenated palm or rapeseed oils.
The expression modified vegetable oil denotes either alkoxylated vegetable oils and in particular ethoxylated and/or propoxylated vegetable oils, or alkoxylated alkyl esters of the oils and in particular ethoxylated and/or propoxylated methyl, ethyl, linear or branched propyl, or linear or branched butyl esters. According to a specific aspect of the present invention, the ethoxylated oils or the ethoxylated alkyl esters of vegetable oils each have an ethylene oxide number, called in the text which follows EO value, of between 1 and 50.
The subject of the invention is more particularly a composition as defined above which comprises at least one ethoxylated methyl ester of a vegetable oil having an EO value of between 1 and 4, more particularly of equal to 1 or 2 and at least one unmodified oil. According to a most specific aspect of the present invention, the composition comprises an ethoxylated methyl ester of a vegetable oil and the same vegetable oil which is unmodified. The ester of ethoxylated vegetable oil/unmodified vegetable oil weight ratio is in general between 1/50 and 50/1 and more particularly between 1/9 and 9/1.
The subject of the invention is also more particularly a composition comprising at least one plant-protection active ingredient, at least one ethoxylated vegetable oil having an EO value of between 10 and 40 and more particularly greater than or equal to 15 and less than or equal to 30, and at least one unmodified oil. According to a most specific aspect of the present invention, the composition as defined above comprises an ethoxylated vegetable oil, and the same vegetable oil which is unmodified. The ethoxylated vegetable oil/unmodified oil weight ratio is generally between 1/50 and 50/1 and more particularly between 1/9 and 9/1.
To improve its stability in the cold, the alkoxylated oil may be prepared by incorporating, before its alkoxylation, from 1 to 10% by weight of glycerol. This problem may also be solved by combining, in the same composition, an alkoxylated vegetable oil as defined above and an alkoxylated alkyl ester of vegetable oil, as defined above, and more particularly an ethoxylated and/or propoxylated methyl, ethyl, linear or branched propyl, or linear or branched butyl ester of a vegetable oil and, more particularly, by combining an ethoxylated vegetable oil having an EO value of between 10 and 40 and preferably greater than or equal to 15 and less than or equal to 30, with an ethoxylated methyl ester of a vegetable oil having an EO value of between 1 and 4, preferably equal to 1 or 2.
According to a final aspect of the present invention, its subject is a modified vegetable oil capable of being obtained by mixing, in the presence of a basic catalyst, from 1 to 10 parts of glycerol per 100 parts of an unmodified vegetable oil chosen from sunflower oil, linseed oil, castor oil, soybean oil, corn oil, groundnut oil, copra oil, olive oil, palm oil or hydrogenated palm oil, and then alkoxylating the resulting mixture; and more particularly a modified vegetable oil as defined above for which the average degree of ethoxylation is approximately greater than or equal to 10, preferably greater than or equal to 15, and less than or equal to 40, and preferably less than or equal to 30. The following examples illustrate the invention without, however, limiting it.